Newbold LK, Oliver AE, Booth T, Tiwari B, DeSantis T, Maguire M, Andersen G, Gast CJ, Whiteley AS
picoplankton, picoeukaryotes, RubisCO, 11 m3, mesocosm, Bergen, Espegrend, Norway, acidification
Since industrialization global CO2 emissions haveincreased, and as a consequence oceanic pH is predictedto drop by 0.3–0.4 units before the end ofthe century – a process coined ‘ocean acidification’.Consequently, there is significant interest in how pHchanges will affect the ocean’s biota and integralprocesses. We investigated marine picoplankton(0.2–2 mm diameter) community response to predictedend of century CO2 concentrations, via a ‘high-CO2’ (~ 750 ppm) large-volume (11 000 l) containedseawater mesocosm approach. We found little evidenceof changes occurring in bacterial abundance orcommunity composition due to elevated CO2 underboth phytoplankton pre-bloom/bloom and post-bloomconditions. In contrast, significant differences wereobserved between treatments for a number of keypicoeukaryote community members. These data suggesteda key outcome of ocean acidification is a morerapid exploitation of elevated CO2 levels by photosyntheticpicoeukaryotes. Thus, our study indicatesthe need for a more thorough understanding ofpicoeukaryote-mediated carbon flow within oceanacidification experiments, both in relation to picoplanktoncarbon sources, sinks and transfer to highertrophic levels.